Electronic analyte assaying device

ABSTRACT

An improved electronic diagnostic device for detecting the presence of an analyte in a fluid sample comprises a casing having a display, a test strip mounted in the casing, a processor mounted in the casing, and a first sensor mounted in the casing and operatively coupled to the processor. The processor is configured to receive a signal from the first sensor when the device is exposed to ambient light thereby causing the device to become activated. The device includes a light shield that exerts pressure across a width of the test strip to prevent fluid channeling along the length of the test strip. The processor is configured to present an early positive test result reading when a measured value exceeds a predetermined early reading threshold value at any time after a predetermined early testing time period.

CLAIM OF PRIORITY

This application claims priority to U.S. Provisional Application Ser.No. 61/389,050, filed on Oct. 1, 2010, the entire disclosure of which isincorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to diagnostic assays for analytes in a liquidsample. In particular, the invention relates to an improved electronicdevice for detecting an analyte in a body fluid and a method of usingthe device for assay test results.

BACKGROUND OF THE INVENTION

Many types of ligand-receptor assays have been used to detect thepresence of various substances in body fluids, such as urine, saliva, orblood. Many of these assays are designed to make a quantitativedetermination, but in many circumstances all that is required is aqualitative positive/negative indication. Examples of such qualitativeassays include blood typing, pregnancy testing, and many types ofurinalysis. For these tests, visually observable indicia, such as thepresence of agglutination or a color change, are preferred.

Qualitative ‘positive/negative’ assays require a high degree ofsensitivity due to the often low concentration of the ligand of interestpresent in the test fluid. False positives can be troublesome,particularly with agglutination and other rapid detection methods suchas dipstick and color change tests. Because of these problems, sandwichassays and other sensitive detection methods which use metal sols orother types of colored particles have been developed.

A common type of device that incorporates the use of such biologicalinteractions is a test strip assay device. U.S. Pat. No. 6,485,982,which is incorporated herein by reference in its entirety, describes adiagnostic device formed of an elongate outer casing which houses aninterior permeable material (such as fiber glass) capable oftransporting an aqueous solution by capillary action, wicking, or simplewetting. The casing defines a sample inlet, and interior regions, whichare designated as a test volume and a reservoir volume. The reservoirvolume is disposed in a section of the test cell spaced apart from theinlet and is filled with sorbent material. The reservoir acts to receiveliquid transported along a flow path defined by the permeable materialand extending from the inlet and through the test volume. In the testvolume is a test site comprising a first protein having a binding sitespecific to a first epitope of the ligand immobilized in fluidcommunication with the flow path (e.g., bound to the permeable materialor to latex particles entrapped in or bonded to the permeable material).A window, such as a hole or transparent section of the casing, permitsobservations of the test site through the casing wall. The method of useof the test cell requires the use of a conjugate comprising a secondprotein bound to colored particles, such as a metal sol or colloid,preferably gold. U.S. Pat. No. 7,045,342, which is incorporated hereinby reference in its entirety, describes an improved diagnostic deviceincluding a test strip comprising of a biphasic chromatographic medium.The biphasic chromatographic medium is formed of a release medium joinedto a capture medium located downstream of the release medium. Therelease and capture media preferably comprise two different materials,or phases, having different specific characteristics. The two phases arejoined together to form a single liquid path such that a solvent frontcan travel unimpeded from the proximal (upstream) end of the releasemedium to the distal (downstream) end of the capture medium.

A purely visual (i.e., human eye dependent) diagnostic test asexemplified above requires proper interpretation of the results.However, devices have been developed to provide an automated detectorsystem for determining sufficient color development at a test site andfor also ensuring that the color intensity is read/interpreted at theappropriate time after sample application. For example, U.S. Pat. No.5,837,546 discloses an integrated reader and a test-strip wherein thetest strip is provided with additional electrodes which sense thepresence of fluid on the test strip which generates a signal to switchon the sensing electronics. The device includes a housing having anexterior surface and defining an interior area. A sample receptorreceives the sample. Reagents on a test strip react with the sample toyield a physically detectable change which correlates with the amount ofselected analyte in the sample. A detector responds to the physicallydetectable change and produces an electrical signal which correlates tothe amount of the selected analyte in the sample. A processor convertsthe electrical signal to a digital output. In another example, U.S. Pat.No. 7,220,597 discloses an integrated reader with a test-strip activatedby a mechanical switch means, wherein the switch means is responsive tothe removal of a lid from the device housing. The device also requires asample sensor for detecting the presence of the sample, wherein samplepresence signal generates a time delay, and a reaction sensor responsiveto the time delay for detecting an analyte in the fluid sample.

Although diagnostic devices, such as those described above, showimprovements over the art, there still remains a need for test devicesproviding greater accuracy and sensitivity. For example, in the field ofpregnancy testing, accurate and rapid detection of low levels of hCG isdesired to allow consumers to confirm pregnancy soon after conceptionhas occurred.

SUMMARY OF THE INVENTION

The present invention recognizes and addresses disadvantages of priorart constructions and methods. Various combinations and sub-combinationsof the disclosed elements, as well as methods of utilizing same, whichare discussed in detail below, provide other objects, features, andaspects of the present invention.

In one preferred embodiment of the present invention, a diagnosticdevice for detecting the presence of an analyte in a fluid samplecomprises a casing having a display, a test strip mounted in the casing,a processor mounted in the casing, and a first sensor mounted in thecasing and operatively coupled to the processor. The processor isconfigured to receive a signal from the first sensor when the device isexposed to ambient light thereby causing the device to become activated.

In some embodiments, when the device is activated, the device performs aself-diagnostic test to ensure that the device is operating withinpre-established parameters.

In other embodiments, the device further comprises a light sourcemounted in the casing and operatively coupled to the processor, thelight source configured to illuminate a portion of the test strip. Insome of these embodiments, a second sensor is mounted in the casing andis operatively coupled to the processor, the second sensor beingpositioned to sense an area corresponding to a test result site on thetest strip. In still other of these embodiments, a third sensor ismounted in the casing and operatively coupled to the processor, thethird sensor being positioned to sense an area adjacent to the testresult site on the test strip. In yet other of these embodiments, theprocessor is configured to receive a signal from the second and thirdsensor, and perform a comparison of the second sensor signal readingwith the third sensor signal reading. The comparison further comprisingcalculating a difference value by subtracting one of the second sensorsignal reading and the third sensor signal reading from the other of thesecond sensor signal reading and the third sensor signal reading.

In yet other embodiments, the processor is configured to confirm thedetection of a valid fluid front when the difference value exceeds apredetermined valid fluid front threshold value. In still otherembodiments, the processor is configured to display a positive testresult message on the display if the difference value is greater than anearly result threshold value at any time after a predetermined timeperiod from the detection of a valid fluid front. In some of theseembodiments, the predetermined time period is less than a standard timeperiod. In one of these embodiments, the predetermined time period isapproximately 90 seconds.

In still other preferred embodiments, the processor is configured todisplay at a predetermined time period from the detection of a validfluid front a positive test result message on the display if thedifference value exceeds a predetermined threshold value and a negativetest result message on the display if the difference value is less thanthe predetermined threshold value. In still other embodiments, thepredetermined time period is approximately 3 minutes.

In some preferred embodiments, a light shield is mounted in the casing,wherein the light shield is configured to apply pressure across a widthof the test strip to prevent channeling of fluid flow along a length ofthe test strip. In some of these embodiments, the light shield furthercomprises a first through hole configured to direct light from the lightsource onto a portion of the test strip, and a second through holeconfigured to direct reflected light from the portion of the test stripto the second sensor and the third sensor.

In still other embodiments, a sample receiving member is coupled to thetest strip at a first end for receiving a fluid sample on the teststrip. In other embodiments, the light source is a light emitting diode,and the first and the second sensors are photo sensors.

In one preferred method for detecting the presence of an analyte in afluid sample, the method comprising the steps of providing a diagnosticdevice comprising a casing having a display, a test strip mounted in thecasing, a processor mounted in the casing, and a first sensor mounted inthe casing and operatively coupled to the processor, the sensor beingconfigured to provide a signal to the processor when the first sensordetects ambient light. The method also comprises the step of coveringthe diagnostic device so as to prevent the first sensor from sensingambient light thereby preventing the diagnostic device from activating.

In some embodiments, the method further comprises the step of activatingthe device when the cover is removed and the first sensor is exposed toambient light. In some of these embodiments, the method furthercomprises the step of performing a diagnostic self-test after the stepof activating to ensure the device is operating within pre-establishedparameters.

In some embodiments, the step of covering comprises of covering a lightport on the casing of the device for directing ambient light to thefirst sensor. In some embodiments, the step of covering furthercomprises sealing the diagnostic device in a light impervious material.In some of these embodiments, the light impervious material is a foilwrapper.

In still other embodiments, the method further comprises the steps ofproviding a light source mounted in the casing that is operativelycoupled to the processor, wherein the light source is configured toilluminate a portion of the test strip, providing a second sensormounted in the casing and operatively coupled to the processor whereinthe second sensor is positioned proximate the test strip so as to sensean area corresponding to a test result site, providing a third sensormounted in the casing and that is operatively coupled to the processor,wherein the third sensor is positioned proximate the test strip so as tosense an area adjacent to the test result site, illuminating the teststrip with the light source, receiving a signal by the processor fromthe second and third sensors, and performing a comparison of the secondsensor signal reading with the third sensor signal reading, wherein thecomparison further comprises calculating a difference value bysubtracting the signal readings from the sensors.

In some of these embodiments, the method further comprises the step ofdisplaying a positive test result message on the display when the signalreading is greater than an early result threshold value at any timeafter a predetermined time period. In yet other of these embodiments,the early result threshold value is greater than a normal predeterminedthreshold value and the time period is less than a standard time period.

In still other embodiments, the method further comprises the step ofminimizing the effect of fluid channeling along the length of the teststrip by providing pressure across the width of the test strip. In someof these embodiments, the pressure across the width of the test strip isprovided by a light shield placed in contact with the test strip.

In another preferred embodiment of a diagnostic device for detecting thepresence of an analyte in a fluid sample, the device comprises a casinghaving a display, a test strip mounted in the casing, the test striphaving a length and a width and a test result site located thereon, alight shield mounted in the casing adjacent the test strip, the lightshield having at least two through holes formed therein, a processormounted in the casing, a sensor mounted in the casing adjacent one ofthe at least two through holes, the sensor being operatively coupled tothe processor, and a light source mounted in the casing adjacent to theother of the at least two through holes, the light source beingoperatively coupled to the processor. A portion of the light shield isconfigured to exert pressure across the width of the test strip toprevent fluid channeling along the length of the test strip.

In some embodiments, a second sensor is mounted in the casing adjacentto one of the at least two through holes, the second sensor beingoperatively coupled to the processor, wherein the derivative iscalculated by subtracting a signal from one of the sensor and the secondsensor from a signal of the other of the sensor and the second sensor.In some of these embodiments, the processor is configured to receive asignal from each of the sensors, and when a derivative of the signals isgreater than an early positive result threshold value at any time aftera predetermined time period, the processor is configured to display apositive result message on the display. In other of these embodiments,the early positive result threshold value is greater than a normalpredetermined threshold value and the predetermined time period is lessthan a standard time period.

In still another preferred embodiment, a diagnostic device for detectingthe presence of an analyte in a fluid sample, the device comprises acasing having a display, a test strip mounted in the casing, the teststrip having a test result site located thereon, a light shield mountedin the casing adjacent the test strip, the light shield having at leasttwo through holes formed therein, a processor mounted in the casing, asensor mounted in the casing adjacent one of the at least two throughholes, the sensor being operatively coupled to the processor and a lightsource mounted in the casing adjacent to the other of the at least twothrough holes, the light source being operatively coupled to theprocessor. In this embodiment, the processor is configured to receive asignal from the sensor indicative of a reading of the test strip testresult site, and when the reading is greater than an early positiveresult threshold value at any time after a predetermined time period,the processor is configured to display a positive result on the display.

In some embodiments, the early positive result threshold value isgreater than a normal predetermined threshold value and thepredetermined time period is less than a standard time period. In otherof these embodiments, the predetermined time period is approximately 90seconds. In still other embodiments, the standard time period isapproximately 3 minutes.

Various combinations and sub-combinations of the disclosed elements, aswell as methods of utilizing same, which are discussed in detail below,provide other objects, features, and aspects of the present invention.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate one or more embodiments ofstacked displays of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, to one of ordinary skill in the art, is set forthmore particularly in the remainder of the specification, includingreference to the accompanying drawings, in which:

FIGS. 1 and 2 are perspective views of the top and left side of thedevice with the cap and with the cap removed, respectively, inaccordance with one embodiment of the present invention;

FIGS. 3 and 4 are respective top and bottom plan views of the device ofFIGS. 1 and 2;

FIGS. 5 and 6 are respective back and front plan views of the device ofFIGS. 1 and 2;

FIGS. 7 and 8 are respective left side and right side plan views of thedevice of FIGS. 1 and 2;

FIG. 9A is an exploded assembly view of the device of FIGS. 1-8;

FIG. 9B is a perspective view of the top and left side of the device ofFIGS. 1-8 with the top half of the casing removed;

FIG. 10A is a schematic top view of a test strip according to oneembodiment for use in the device of FIGS. 1-8;

FIG. 10B is a schematic side view of the test strip of FIG. 10A;

FIG. 11 is a perspective view of the top and left side of the printedcircuit board and display for use in the device of FIGS. 1-8;

FIGS. 12A and 12B are respective top and bottom views of the printedcircuit board of FIG. 11 with battery;

FIG. 12C is a side view of the printed circuit board of FIG. 11;

FIG. 13A is a top view of a light shield for use in the device of FIGS.1-8;

FIG. 13B is a bottom view of the light shield of FIG. 13A;

FIG. 13C is a side view of the light shield of FIG. 13A;

FIG. 13D is a perspective sectional view of the top and left side of theof the light shield of FIG. 13A;

FIG. 14A is a partial left side sectional view of the device of FIG. 9B;

FIG. 14B is a partial right side sectional view of the device of FIG.9B;

FIG. 15 illustrates a flow process carried out by the device of FIGS.1-8 during assembly.

FIG. 16 illustrates a flow process carried out by the device of FIGS.1-8 while the device is waiting for receipt of a fluid sample.

FIGS. 17A-C are graphical illustration of test results.

Repeat use of reference characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention according to the disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to presently preferred embodimentsof the invention, one or more examples of which are illustrated in theaccompanying drawings. Each example is provided by way of explanation,not limitation, of the invention. It is to be understood by one ofordinary skill in the art that the present discussion is a descriptionof exemplary embodiments only, and is not intended as limiting thebroader aspects of the present invention, which broader aspects areembodied in the exemplary constructions. In fact, it will be apparent tothose skilled in the art that modifications and variations can be madein the present invention without departing from the scope and spiritthereof. For instance, features illustrated or described as part of oneembodiment may be used on another embodiment to yield a still furtherembodiment. Thus, it is intended that the present invention covers suchmodifications and variations as come within the scope of the appendedclaims and their equivalents.

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the inventions are shown. Indeed, the invention may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. As used in the specification, the singular forms “a,”“an,” “the,” include plural referents unless the context clearlydictates otherwise.

The invention comprises of an electronic device for conducting animmunoassay and a method of using the device. The inventive device ischaracterized in that it provides an opto-electronic processing means inan improved single-step device that increases the efficiency andeffectiveness of a simplified test that untrained personnel can use toreliably assay a liquid sample for the presence of extremely smallquantities of a particular ligand with high degree of accuracy. Theinvention is ideal for use in over-the-counter (OTC) diagnostic testkits which will enable a consumer to self diagnose, for example,pregnancy, ovulation, sexually transmitted infections, and otherbacterial infections or clinical abnormalities which result in thepresence of an antigenic marker substance in a body fluid, includingdetermination of the presence of drugs and their metabolites or toxins.The assay process and the test device are engineered specifically todetect the presence of a pre-selected individual ligand present in bodyfluids or other fluids.

The term “body fluid,” as used herein, refers to a sample of biologicalorigin, or a sample derived from the sample of biological origin. Thebiological samples include, but are not limited to, blood, plasma,serum, saliva, cerebral spinal fluid, pleural fluid, milk, lymph,sputum, semen, urine, stool, tear, saliva, needle aspirate, externalsection of the skin, respiratory, intestinal, or genitourinary tract,tumor, organ, cell culture, cell culture constituent, tissue sample,tissue section, whole cell, cell constituent, cytospin, or cell smear.

The inventive device can be used to detect any analyte which hasheretofore been assayed using known immunoassay procedures, or known tobe detectable by such procedures, using polyclonal or monoclonalantibodies or other proteins comprising binding sites for ligands.Various specific assay protocols, reagents, and proteins can be usedaccording to the present invention such as, for example, those describedin U.S. Pat. No. 4,313,734, which is incorporated herein by reference.

As used herein, an “analyte” refers to the material to be detected byuse of the device and method of the present invention. “Analyte”includes but is not limited to: antigens, antibodies, hormones (such asFSH, TSH, hCG, LH), drugs, proteins associated with a cell (“cellproteins”), secreted proteins, enzymes, cell surface or transmembraneproteins, glycoproteins and other proteins, peptides, and carbohydrates.

As used herein, “antibody” refers to a polypeptide substantially encodedby an immunoglobulin gene or immunoglobulin genes, or fragments thereof,which recognizes and binds an antigen. The recognized immunoglobulingenes include the kappa, lambda, alpha, gamma, delta, epsilon, and muconstant region genes, as well as the immunoglobulin variable regiongenes. Antibodies include fragments, such as Fab′, F(ab)2, Fabc, and Fvfragments. The term “antibody,” as used herein, also includes antibodyfragments either produced by the modification of whole antibodies orthose synthesized de novo using recombinant DNA methodologies, andfurther includes “humanized” antibodies made by now conventionaltechniques.

As used herein, a “capture antibody” should be understood as anantibody, such as a monoclonal or polyclonal antibody, attached directlyor indirectly to a substrate, such as a solid phase. The captureantibody can include at least one binding member that recognizes andbinds a particular, distinct epitope of an antigen, such as hCG.Embodiments of the present invention preferably also make use of aconjugate (labeled binding member) comprising an antibody bound to adetectable label component (which can be colored particles, such as ametal sol or colloid, preferably gold).

The diagnostic device of the invention preferably makes use of aconjugate comprising a protein bound to a label component. Anydetectable label recognized in the art as being useful in various assayscould be used in the present invention. In particular, the detectablelabel component can include compositions detectable by spectroscopic,photochemical, biochemical, immunochemical, or chemical means. The labelcomponent thus produces a detectable signal. Exemplary labels includefluorescent dyes, chemiluminescent compounds, radioisotopes,electron-dense reagents, enzymes, or colored particles (such as a metalsol or colloid, preferably gold). The label component can generate ameasurable signal, such as radioactivity, fluorescent light, color, orenzyme activity, which can be used to identify and quantify the amountof label bound to a test site. Thus, the label component can alsorepresent the presence of a particular antigen bound thereto.

The assay can take two distinct forms, depending on whether the assay isdesigned to exploit the “sandwich” or “competitive” technique. Inembodiments wherein the device of the invention makes use of a sandwichtechnique, the antibody used in the detection comprises a binding regionor site which binds to an epitope on the analyte for detection, such ashCG. The antibody designated as label antibody preferably has a labelcomponent bound thereto to form a labeled conjugate (labeled bindingmember), which reacts with the analyte of interest to form a complex inthe liquid sample. The analyte bound to the conjugate (labeled bindingmember) reacts with a second antibody designated as capture antibody toform a “sandwich” of the capture antibody, analyte, and conjugateantibody (labeled binding member). In certain embodiments, abiotinylated capture antibody can also be utilized. For example, thebiotinylated capture antibody can include a region or site that binds toa second epitope on the analyte. In these embodiments, the resulting“sandwich” comprises a complex of the labeled conjugate {labeled bindingmember}-analyte-{biotinylated capture antibody}. In general, the“sandwich” complex is progressively produced as the biological samplewith the analyte therein continuously moves along the test strip of thedevice. As more and more “sandwich” complexes are immobilized at thecapture site (test site) comprising of a binding member with affinity tothe biotinylated capture antibody, the label components aggregate andare detected using an electronic sensor, indicating the presence of aparticular analyte in the biological sample. The electronic sensor maybe photo-optic or it can be other types and kinds of sensors, includingmagnetic sensors. When magnetic sensors are used, then magneticparticles are employed on the test strip.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassedwithin the invention. The upper and lower limits of these smaller rangesmay independently be included or excluded in the range, and each rangewhere either, neither or both limits are included in the smaller rangesis also encompassed within the invention, subject to any specificallyexcluded limit in the stated range. Where the stated range includes oneor both of the limits, ranges excluding either or both of those includedlimits are also included in the invention.

Referring to FIGS. 1-8, a schematic illustration of an embodiment ofdevice 10 is shown constructed in accordance with one embodiment of thepresent invention. Device 10 comprises of a molded top casing 18 and abottom casing 22, which collectively define a hollow, elongateenclosure. A removable cap 14 is secured to one end of the casingenclosure over a sample receiving member 16. Sample receiving member 16is positioned so that part of the sample receiving member is received inthe casing enclosure and part of the sample receiving member extendsfrom the end of the casing enclosure.

The top casing (FIGS. 1-3) is configured to provide a recessed portion20 shaped to permit users to place their thumb into the recessed portionand their forefinger on bottom casing 22 (FIG. 4) to securely holddevice 10. A raised central section (FIGS. 1-3) of top casing 18 definesa centrally located window 26 to permit a user to observe test resultsprovided on an underlying display 28 (e.g. LCD).

Referring to FIG. 5, a battery removal tab 30 is formed therein to allowthe user to open the device to properly dispose of the battery therein.

It should be understood that the above description of a device is forillustrative purposes, and other devices may be used.

Referring to FIG. 9A, the device is shown having a bottom case 22, a topcase 18, a sample receiving member 16, a test strip 32, a light shield46, a printed circuit board 27, a battery 31 and a desiccant 24.Referring to FIG. 9B, sample receiving member 16 and test strip 32 arereceived in bottom casing 22. Sample receiving member 16, in addition toproviding a means for receiving the sample also serves as a filter whichcan remove from test samples particulate matter and interfering factors.The sample receiving member is preferentially disposed within the casingenclosure and extends to the exterior thereof. In one preferredembodiment, sample receiving member 16 preferably is a bibuloushydrophilic material which facilitates absorption and transport of afluid sample to test strip 32. As taught in U.S. Pat. No. 6,277,650,such materials may include cellulose acetate, hydrophilic polyester, andother materials having similar properties.

Various alignment structures (FIG. 9A not shown) are used to properlyseat the sample receiving member 16 and test strip 32 in bottom casing22 (FIG. 9B). Test strip 32 comprises of alignment hole 40 (FIG. 10A)formed towards the distal end of the test strip configured to receivealignment pin 29 on bottom casing 22 (FIG. 9B). Light shield 46 alsocomprises an alignment hole 74 (FIG. 13A) configured to receivealignment pin 29 on bottom casing 22, such that light shield 46 isposition over test strip 32 (FIG. 9B). Also, a variety of alignmentguides 21 maintain the light shield in correct alignment with test strip32 and printed circuit board 27. Printed circuit board 27 has display 28operatively connected on one side thereof. Printed circuit board 27 ismaintained in alignment with the various other parts of test device 10using alignment guides 21 and various alignment recesses 23. Mating ofalignment guides 21 and alignment recesses 23 maintain properpositioning of the printed circuit board with respect to the test strip,the bottom casing and the top casing so that display 28 properly alignswith top casing window 26. A battery 31 is operatively coupled toprinted circuit board 27 and provides power for all electrical parts ofdevice 10.

Also, the preferred embodiment of the invention includes a test strip 32comprising of a triphasic chromatographic medium. For ease ofillustration, reference is made to FIGS. 10A and 10B. The triphasicchromatographic medium includes a release medium 38 and a reservoir pad36 adjacent the capture medium 34. As taught in U.S. Pat. No. 6,277,650,a release medium 38 preferably comprises absorbent paper, and thecapture medium 34 preferably comprises a nitrocellulose membrane. Alsoshown herein and as taught in the aforesaid patent, the release medium38, the capture medium 34 and the reservoir pad 36 preferably arelaminated onto an opaque plastic film or sheet 42 (FIG. 10B). Disposedupon the release medium 38 is a first binding member comprising a firstmonoclonal antibody reactive with a first epitope on the analyte, andlabeled with a visually detectable marker, such as, colloidal goldparticles, and a capture component comprising a biotinylated monoclonalantibody disposed downstream of the labeled antibody. The biotinylatedantibody is reactive with a second epitope on the analyte and is capableof forming a complex with the labeled antibody and the analyte. Alsodisposed upon the capture medium is a site for capturing andimmobilizing the complex, as previously mentioned. The capture siteimmobilizes thereon a capture component, preferably streptavidin, whichhas a high affinity for the biotin portion of the complex.

A method for manufacturing the preferred triphasic chromatographicmedium is described in U.S. Pat. No. 5,846,835, the disclosure of whichis incorporated herein by reference.

The preferred embodiment of test strip 32 further comprises, a reservoirpad 36 consisting of absorbent material disposed distal to, ordownstream of capture medium 34 and in fluid communication therewith.The purpose of the reservoir pad 36 is to facilitate capillary actionalong the chromatographic substrate of test strip 32, and to absorbexcess fluid sample contained with the device 10. The reservoir padabsorbent material preferably comprises absorbent paper made from cottonlong linter fibers, such as identified by product codes S&S 300, S&S470, and S&S 900 (available from Schleicher & Schuell, Inc.) orcellulosic materials, such as Whatman 3MM (available from Whatman).Referring to FIG. 10B, a side view of one embodiment of the test strip32 is shown where the distal or downstream end of release medium 38overlaps the proximal or upstream end of capture medium 34 and thedistal or downstream end of capture medium 34 overlaps the proximal orupstream end of reservoir pad 36. Again, release medium 38 and thecapture medium 34 may alternatively be connected via a butt joint ratherthan being in overlapping connection. These three components arelaminated on a plastic backing and together form a single fluid path,and cooperate to cause sample liquid to flow along release medium 38 andthe capture medium 34 into reservoir pad 36.

FIGS. 11 and 12A-12C, printed circuit board 27 is generally rectangularin shape and defines a plurality of alignment recesses 23 formedthereon. Display 28 is mounted on one side of printed circuit board 27and is operatively coupled to a processor 48 (FIG. 12B) mounted on anopposite side of printed circuit board 27. Referring to FIG. 12B, alight source 50 is mounted on printed circuit board 27, which in onepreferred embodiment is a light emitting diode (LED), but in otherembodiments may be any suitable light source. In addition to lightsource 50, two light sensors 52 and 54 are mounted proximate to lightsource 50 on printed circuit board 27. Light sensors 52 and 54, in onepreferred embodiment, are photo sensors. Light source 50 and photosensors 52 and 54 are operatively coupled to processor 48. Battery 31 isreceived between a first terminal 56 and a second terminal 62. Firstterminal 56 is formed from a metal contact material and includes twoidentical fingers 60. First terminal 56 may be formed from any suitableconductive material and in one preferred embodiment is formed from aspring steel material. Second terminal 62 may be integrally formed onprinted circuit board 27 or may be formed from a conductive materialthat is attached to printed circuit board 27. In either case, terminals56 and 62 provide electrical energy from battery 31 to processor 48 andthe various other electrical components on printed circuit board 27.

Still referring to FIG. 12B, a light photo sensor 53, in a preferredembodiment a photo sensor, is mounted on printed circuit board 27. Photosensor 53 is mounted on an opposite end of processor 48 and photosensors 52 and 54, and is configured to seat adjacent a light port 12(FIG. 4) formed in bottom casing 22. Photo sensor 53 is operativelycoupled to processor 48 such that when photo sensor 53 detects ambientlight device activates and runs a self-diagnostic test to ensure thatthe device is operating within pre-established parameters. Thus, unlikemechanical and fluid mechanisms used to activate prior art electronicassay devices, device 10 uses photo sensor 53, which is ported to thebottom casing exterior by light port 12 to detect ambient light (asshown in FIG. 4).

In one preferred embodiment, when device 10 is manufactured, light port12 is covered to prevent ambient light from reaching photo sensor 53thereby preventing device 10 from activating. Preventing photo sensor 53from sensing ambient light may be accomplished by taping over light port12 opening or by placing device 10 into a light impervious wrapper orpouch. For purposes of the present invention, the terms “wrapper” or“pouch” should be broadly construed to mean a foil wrapper, a box, asleeve, a tube or any other suitable receptacle or covering that islight impervious and that prevents ambient light from reaching photosensor 53.

Once device 10 is packaged, the device is maintained in sleep mode untila user opens the wrapper thereby allowing ambient light to reach thephoto sensor. Upon detecting ambient light, a signal is communicatedfrom photo sensor 53 to processor 48, which is configured to activatetest device 10 and run at least one diagnostic test and display a“clock” icon on the LCD screen. In testing several thousand devices,this method of activation has proven to be extremely reliable, with nodevice failures due to the activation technology. Upon deviceactivation, display 28 shows a “clock” icon which provides the user witha visual aid to confirm that the device is ready for use.

Referring to FIGS. 13A-13D, light shield 46 is shown having a first end46A and an opposite second end 46B. A top surface 64 of light shield 46defines a first through hole 66 and two additional through holes 68A and68B. Through holes 66 and 68A and 68B are positioned in light shield 46so that they align with test result site on capture medium 34. Opposingrails 70 formed on a bottom surface 72 of light shield 46 assist inaligning the light shield with test strip 32. Additionally, a hole 74 isconfigured to receive bottom casing pin 29 (FIG. 9B) to also guide lightshield 46 into proper alignment with test strip 32. The light shield 46as shown in FIGS. 13A-13D also includes an aperture 58 which aligns withlight port 21 of bottom casing 22 to direct ambient light to photosensor 53 on printed circuit board 27. Referring in particular to FIG.13D, first through hole 66 is separated from the additional throughholes 68A and 68B by a first common wall 76. First common wall 76 beginsfrom light shield top surface 64 and extends downward most but not allthe way to light shield bottom surface 72. Again referring to FIG. 13D,a second common wall 78 separates through hole 68A from through hole 68Band extends from light shield top surface 64 to light shield bottomsurface 72. First common wall 76 prevents light from light source 50from shining directly onto photo sensors 52 and 54, while second commonwall 78 prevents sensor cross-contamination or cross-talk between photosensors 52 and 54. Light shield 46 is mounted intermediate printedcircuit board 27 and bottom casing 22 (as shown in FIG. 9B). Test strip32 is positioned intermediate light shield 46 and bottom casing 22 sothat first through hole 66 aligns with light source 50 and additionalthrough holes 68A and 68B align with photo sensors 52 and 54,respectively. Various areas 80 of light shield 46 are configured toexert pressure across a width of test strip 32. Lateral pressure acrosstest strip 32 helps to prevent channeling of fluid flow along the lengthof test strip 32. To assist in maintaining pressure exerted by lightshield 46 on test strip 32, a flange 82 may be formed on light shieldtop surface 64, which is configured to engage top casing 18 when topcasing 18 and bottom casing 22 are attached to one another.

Referring to FIGS. 14A and 14B, the relative position of light shield 46and test strip 32 is shown. Referring in particular to FIG. 14A, bottomcasing alignment pin 29 engages test strip 32, light shield 46 (notshown in figure due to partial cutaway view) and printed circuit board27 to maintain the longitudinal positioning of these components withrespect to one another and bottom casing 22. The longitudinalpositioning maintains through holes 68A and 68B (FIG. 13D) in alignmentwith respective photo sensors 52 and 54 on the printed circuit board.That is, sensor 52 aligns with through hole 68A and test result site,and sensor 54 aligns with through hole 68 Band area adjacent the testresult site. Referring particularly to FIG. 14B, light shield throughhole 66 aligns with light source 50 on printed circuit board 27. In thepreferred embodiment, light source 50 is a light emitting diode (LED)and is configured to illuminate both test result site and area adjacentthe test result site. Use of an LED provides a very strong light sourcethat acts to normalize the effect of ambient light that may penetratefrom outside the housing. If the LED light source is not adequatelycontrolled, outside ambient light can interfere with the interior LEDlight and affect the test result. Moreover, use of a single LED alsoeliminates the possibility of intensity variability that occurs inmultiple LED systems.

First common wall 76, positioned intermediate through holes 68A and 68Band through hole 66, prevents light from light source 50 from shiningdirectly onto photo sensors 52 and 54. Moreover, second common walls 78prevents light from test result site from reflecting onto photo sensor54 and conversely light from area adjacent the test result site fromreflecting onto photo sensor 52. In this way, there is no crosscontamination of reflected light from the test result site and the areaadjacent the test result site on the photo sensors.

As previously stated, light sensors 52 and 54 are photo sensors thattarget respectively test result site and area adjacent the test resultsite. Area adjacent the test result site is used to establish abackground measurement for use in determining the level of analytepresent in the fluid sample. Use of dual photo sensors provides moreaccurate measurement of the target areas to better evaluate test linecolor and migration of the labeled binding member for determining thevalidity of a test result. Effectiveness of the differentiation betweentest result site and area adjacent the test result site is optimized toimprove accuracy through enhancement of both the distance between photosensors 52 and 54 and the position of light source 50 with respect tothe photo sensors.

Referring to FIG. 14B, light is emitted from light source 50 directlyonto both test result site and area adjacent the test result site.Referring to FIG. 14A, the projected light from light source 50 reflectsoff of the test result site and area adjacent the test result site oncapture medium 34, and is directed via the respective walls of thethrough holes onto photo sensors 52 and 54 sensors. Each photo sensorgenerates an electrical signal based on the magnitude of the reflectedlight received by the photo sensor. The electrical signals areoperatively communicated to processor 48 where the signals are digitizedand computed by the processor. The signals received from photo sensorsare representative of the amount of labeled binding member captured attest result site, and of a background reading from the area adjacent thetest result site, In one preferred embodiment, the computation comprisesthe step of subtracting a value representative of the test result sitesignal from a value representative of the adjacent area signal. Theprocessor than compares the resultant value to predetermined thresholdvalues stored in memory in a lookup table to determine whether one of aplurality of test results has been met. Referring to FIG. 15, the flowprocess carried out by the processor 48 during assembly of the device isshown. At step 84, processor 48 runs a program consisting ofinitializing memory, registers, and I/O ports. The processor thenchecks, at step 86, whether the device powered up normally. If not, atstep 98, the device displays an invalid message. If power up was normal,then at step 88 the processor inhibits brownout and a self-test iscarried out, at step 90. If the self-test was unsuccessful, then at step98 the device displays an invalid message. Otherwise, at step 92,display 28 displays “YES+” and “clock” icons. Processor 48 then waitsfor a predetermined time period, which in one embodiment is 24 hours, todetermine and confirm that no activation signal (e.g. ambient light) ispresent, at step 96. If an activation signal is present, then at step 98the device displays an invalid message. Otherwise in the absence of anactivation signal display 28 is cleared, at step 100, and the deviceenters a deactivated (Sleep) mode at step 102.

Referring to FIG. 16, device 10 is activated at step 104 once thewrapper, covering or packaging of the device has been opened and ambientlight is detected by photo sensor 53. At step 106, the processor causesall icons to blink for a brief period on display 28. Afterwards at step108, RAM memory is initialized, brownout (low voltage condition)detection is carried out, and the “clock” icon is displayed. At step110, a self-test is performed. If errors are detected, an invalidmessage is displayed at step 98. Otherwise, at step 112, the systemwaits for detection of a fluid front on test strip 32. Following thedetection of the fluid front at step 114, the system monitors themigration of the labeled binding member to determine that a valid fluidfront is present. If not, then at step 98 the device displays an invalidmessage. If, on the other hand, a valid fluid front is detected, the“clock” icon blinks on display 28 as the device waits for the testresults at step 118. Once results are determined at step 118, theresults are displayed at step 120.

FIGS. 17A-C show graphical representations of typical readings (i.e.calculated values) against time of a testing cycle following deviceactivation and sample application. In FIGS. 17A-C, a calculated valueexceeding a fluid front threshold indicates that a fluid sample has beendetected. Subsequently thereafter, a calculated value exceeding a validfluid front threshold indicates that a valid sample has been detectedand the device is operating. The calculated signal then drops and levelsoff. At this point in the testing cycle, the calculated signal mayresemble one of the three graphs illustrated in FIGS. 17A-C. FIG. 17Aillustrates a positive test result occurring at the standard test resulttime period when the calculated value exceeds the normal predeterminedthreshold value but is below the early positive result threshold value.FIG. 17B illustrates a negative result occurring at the standard testresult time period when the calculated value is below the normalpredetermined threshold value. FIG. 17C illustrates an early positiveresult occurring anytime between the early positive Lest result timeperiod and the standard test result time period when the calculatedvalue exceeds the early positive result threshold value.

In some preferred embodiments, device 10 may also have a logger systemconfigured to download critical data from the microcontroller duringprepackage testing or post use testing. The capability to download datais critical especially for trouble-shooting and product developmentpurposes. Additionally, this logger system can be used duringmanufacturing as a quality control tool.

EXPERIMENTAL

The performance of finished devices was verified and validated through aseries of studies summarized as follows:

Analytical Sensitivity

Fifty (50) devices were tested to determine the endpoint sensitivity andgeneral functionality. Devices were dipped such that the samplereceiving member was submerged in an hCG standard prepared in poolednegative urine for 5 seconds. Specifically, ten (10) devices were dippedin 0 mIU/mL and 5 mIU/mL of hCG standard, respectively, and fifteendevices (15) were dipped in 10 mIU/mL and 20 mIU/mL of hCG standard,respectively. The results summarized in Table 1 illustrate that apositive result is consistently produced in devices tested in standardswith an hCG concentration of 10 mIU/mL and above.

TABLE 1 Analytical sensitivity Mean Time for Result hCG Std. DisplayedResult (min:sec)  0 mIU/mL 10/10 NO− 3:28 (Range = 3:25-3:29)  5 mIU/mL 6/10 YES+ 3:24  4/10 NO− (Range = 3:21-3:25) 10 mIU/mL 14/15 YES+ 3:26 1/15 “?” (Range = 3:25-3:36) (invalid) 20 mIU/mL 15/15 YES+ 3:27 (Range= 3:25-3:29)Verification of Device for Early Positive Response

Twenty (20) devices were tested to verify the ability of the device toproduce a result from a positive urine sample earlier than the standard3-minute result time. Devices were dipped in an hCG standard prepared inpooled negative urine as described above. Specifically, ten (10) deviceswere dipped in 10 mIU/mL of hCG standard, and five (5) devices weredipped in 100 mIU/mL and 10,000 mIU of hCG standard, respectively. Theresults summarized in Table 2 illustrate that a positive result isproduced earlier than 3 minutes when devices were tested using standardswith an hCG concentration of 100 mIU/mL and above.

TABLE 2 Early Positive Response Mean Time for Result hCG Std. DisplayedResult (min:sec)    10 mIU/mL 10/10 YES+ 3:23 (Range = 3:21-3:26)   100mIU/mL  5/5 YES+ 1:53 (Range = 1:49-1:58) 10,000 mIU/mL  5/5 YES+ 1:53(Range = 1:51-1:56)Valid Fluid Front Testing

To obtain a valid (YES+/NO−) result, the device must detect a validfluid front by sensing the presence of the label reagent (gold) in thesample as it passes through the detection zone. In the absence ofsensing the presence of the label reagent the device will display a “?”invalid result. This invalid state can be simulated using test stripscontaining all the appropriate reagents but lacking the label reagent.Ten (10) functional devices employing test strips lacking the labelreagent were dipped in an hCG standard prepared in pooled negative urineas described above. Specifically, five (5) devices were dipped in 0mIU/mL and 100 mIU/mL of hCG standard, respectively. The resultssummarized in Table 3 illustrate that, in the absence of the labelreagent, each of the devices yielded a “?” invalid result when testedwith 0 mIU/mL and 100 mIU/mL of hCG standards.

TABLE 3 Valid fluid front testing using label-free test strips Mean Timefor Result hCG Std. Displayed Result (min:sec) 0 and 100 10/10 “?”(invalid) 0:24 mIU/mL (Range = 0:22-0:26)User Testing

When excessive amount of sample is applied to the sample receivingmember in midstream use, a situation referred to as “flooding” may occurwhere the label reagent is not released and therefore does not migratedue to rapid and total saturation of the test strip, or it is diluted bythe rush of sample to a color level below the pre-established validfluid front threshold. To test whether “flooding” occurs, thirty (30)devices were tested by midstream sample application using in-housenon-pregnant volunteer users. The results summarized in Table 3illustrates that a negative result “NO−” was produced in twenty-nine(29) devices, while one (1) device produced an invalid result (“?”) soonafter sample application. The device with the invalid result wasreplaced with a new device and retested by the same volunteer. The newdevice produced “NO−” result during repeat testing for an overallaccuracy of 100%. Electronic data extracted from the device thatproduced an invalid result “?” identified that the cause of the invalidresult was due to the migration of the label (gold) not meeting thevalid fluid front threshold.

TABLE 4 User testing (midstream sample application) Test Strip MeanSample Sample Displayed Result Result Weight (g) midstream 29/30 NO−31/31 1.10 urine  1/30 “?” negative (range 0.87-1.36) (non- Repeattesting of invalid pregnant)  1/1 NO−

While one or more preferred embodiments of the invention are describedabove, it should be appreciated by those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the scope and spirit thereof. It is intended thatthe present invention cover such modifications and variations as comewithin the scope and spirit of the appended claims and theirequivalents.

We claim:
 1. A diagnostic device for detecting the presence of ananalyte in a fluid sample, the device comprising: a casing having adisplay; a test strip mounted in said casing; a battery mounted in saidcasing; a processor mounted in said casing coupled to said battery; alight source mounted in said casing and operatively coupled to saidprocessor, said light source configured to illuminate a portion of saidtest strip; a first sensor mounted inside said casing coupled to saidbattery and operatively coupled to said processor; and an opening insaid casing through which the first sensor can receive ambient light;wherein said processor is configured to receive a signal from said firstsensor when said device is exposed to ambient light thereby causing saiddevice to become activated.
 2. The device of claim 1, wherein when saiddevice is activated, said device performs a self-diagnostic test toensure that the device is operating within pre-established parameters.3. The device of claim 1, further comprising a second sensor mounted insaid casing and operatively coupled to said processor, said secondsensor being positioned to sense an area corresponding to a test resultsite on said test strip.
 4. The device of claim 3, further comprising athird sensor mounted in said casing and operatively coupled to saidprocessor, said third sensor being positioned to sense an area adjacentto the test result site on said test strip.
 5. The device of claim 4,wherein said processor is configured to: receive a signal from saidsecond and third sensors; and perform a comparison of said second sensorsignal reading with said third sensor signal reading, wherein saidcomparison further comprises calculating a difference value bysubtracting one of said second signal reading and said third signalreading from the other of said second signal reading and said thirdsignal reading.
 6. The device of claim 5, wherein said processor isconfigured to confirm the detection of a valid fluid front when saiddifference value exceeds a predetermined valid fluid front thresholdvalue.
 7. The device of claim 5, wherein said processor is configured todisplay a positive test result message on said display if saiddifference value is greater than an early positive result thresholdvalue at any time after a predetermined time period from the detectionof a valid fluid front.
 8. The device of claim 7, wherein saidpredetermined time period is less than a standard time period.
 9. Thedevice of claim 8, wherein said predetermined time period isapproximately 90 seconds.
 10. The device of claim 5, wherein saidprocessor is configured to display within a predetermined time periodfrom the detection of a valid fluid front a positive test result messageon said display if said difference value exceeds a predeterminedthreshold value, and a negative test result message on said display ifsaid difference value is less than said predetermined threshold value.11. The device of claim 10, wherein said predetermined time period isapproximately 3 minutes.
 12. The device of claim 1, further comprising alight shield mounted in said casing, wherein said light shield isconfigured to apply pressure across a width of said test strip toinhibit uneven channeling of fluid flow along a length of said teststrip.
 13. The device of claim 4, further comprising a light shieldmounted in said casing, wherein said light shield is configured to applypressure across a width of said test strip to prevent channeling offluid, said light shield further comprising: a first through holeconfigured to direct light from said light source onto a portion of saidtest strip; and a second through hole configured to direct reflectedlight from said portion of said test strip to said second sensor andsaid third sensor.
 14. The device of claim 1, further comprising asample receiving member coupled to said test strip at a first end forreceiving a fluid sample on said test strip.
 15. The device of claim 3,wherein said light source is a light emitting diode; and wherein saidfirst and said second sensors are photo sensors.
 16. The device of claim1, wherein said display is mounted on a first side of said casing andsaid first sensor is mounted on a second side of said casing, saidsecond side being opposite to said first side.
 17. The device of claim1, wherein said casing is elongated.
 18. The device of claim 5, whereinsaid processor is programmed with a normal test result time, a normaltest result threshold, an early test result time, and an early testresult threshold, wherein said processor is configured to provide apositive result message if the difference value exceeds the early testresult threshold after the early test result time and before the normaltest result time, or if the difference value exceeds the normal testresult threshold at the normal test result time.
 19. The device of claim18, wherein the early test result threshold is greater than the normaltest result threshold.